4
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones MJO – North Atlantic Maloney and Hartmann (2000, Science) The MJO is the strongest influencing factor. Mo (2000, J. Climate) Tropical storms are most likely develop and maintain in the Atlantic, when enhanced convection associated with the tropical intraseasonal oscillations is located over the Indian Ocean and convection in the Pacific is suppressed. … Remote circulation response to the MJO-related convection alters the vertical wind shear in the NA. Adapted from Maloney and Hartmann (2000) Active PhaseInactive Phase

8
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones MJO – Western North Pacific Kim et al. (2006, in revision) Major TC passages experience an east-west displacement on intraseasonal timescale according to the phase of the MJO, but not so dramatic as the impact of ENSO. IO phase WNP phase Transition phase + + - -

10
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones MJO – Australia and South Pacific Hall et al. (2001, Monthly Weather Review) The MJO strongly modulates the TC activity in the ASP with pronounced modulation to the northwest of Australia. There are significantly more TCs formed during the active MJO phase. This relationship is strengthened during El Niño periods.

13
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones 10- to 25-day Oscillation – Western North Pacific Northwestward-moving circulation and convection that may be related to the MJO (Hartmann et al. 1992; Kemball-Cook and Wang 2001; Fukutomi and Yasunari 1999, 2002; and many others) Its timescale is overlapped by the westward-moving equatorial Rossby wave. Relationship with TC activity Hartmann et al. (1992, J. Atmospheric Sciences) Typhoons appear to have a preferred recurrence period of between 15 and 25 days, … Harr et al. (from the PPT presented at Taiwan, 11 Dec 2003) The 10-25 day circulations may dominate the MJO to influence TC activity during inactive MJO phases or to influence the timing of TC activity during MJO active periods. The source of the 10-25 day mode is linked to wave activity in the Southern Hemisphere. Cross-equatorial influence from the Southern Hemisphere is possibly related to the AAO (e.g., Ho et al. 2005). Cyclogenesis related to the equatorial Rossby waves seems to reflect this variability (Frank and Roundy 2006, Monthly Weather Review).

15
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – North Atlantic What we know … The western Sahel rainfall is negatively correlated with ENSO events. The activity of AEWs intensifies (weaker) when the rainfall amount over the western Sahel region is above (below) normal. During El Niño years, westerly wind in the upper troposphere increases over the Caribbean and tropical Atlantic, resulting in an increase of the vertical wind shear over the NA. Consequently, the number of TCs and their duration are reduced. Besides, the probability of U.S. hurricane landfalls becomes lower. The QBO influence on TC activity is known to be pronounced in the NA than in other basins. Recently, however, the relationship disappeared from 1984 to the present (Landsea, personal communication). Recent literatures (after 2000) Thorncroft and Hodges (2001, J. Climate), Tang and Neelin (2004, Geophysical Research Letters), Larson et al. (2005, J. Climate), Xie et al. (2005, J. Climate), Bell and Chelliah (2006, J. Climate), etc.

16
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – North Atlantic Thorncroft and Hodges (2001, J. Climate) The 850-hPa easterly wave at the West African coast between about 10°N and 15°N is highly correlated to NA TC activity. The NA TC activity may be influenced by the number of AEWs leaving the West African coast, and not simply by the total number of AEWs. AfricaAtlantic

23
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Western North Pacific What we know … The active genesis region of the TC moves both eastward and toward the equator, the life span and probability of the intense TC increase, and TCs recurve more often and tend to recurve farther eastward during the warm phase of ENSO. The northward steering flows increase in the WNP. There is a notable frequency reduction in TC formation in the summer following of the El Niño year, corresponding to a longitudinal shift of the Walker circulation. The westerly phase of the QBO corresponds to a larger number of TCs. However, this relationship do not hold true during ENSO years. The vertical shear equatorward of 18°N over the eastern portion of the WNP is substantially reduced during El Niño periods. Recent literatures (since 2002) ENSO: Wang and Chan (2002, J. Climate), Elsner and Liu (2003, Climate Research), Camargo et al. (2004, AMS conference), Wu et al. (2004, J. Climate), Camargo and Sobel (2005, J. Climate), etc. More factors: Chia and Ropelewski (2002, J. Climate), Chen et al. (2004, J. Climate), Ho et al. (2005, J. Geophysical Research), Kim et al. (2005, J. Climate), Xie et al. (2005, Geophysical Research Letters), etc.

24
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Western North Pacific Elsner and Liu (2003, Climate Research) The abundance of straight-moving typhoons is a good indicator of the typhoon threat to portions of southern China. The number of straight-moving typhoons is correlated with the ENSO cycle. Camargo et al. (J. Climate, in revision) Specific clusters of typhoon tracks clearly represent the influence of ENSO on TC activity. Camargo and Sobel (2005, J. Climate) Using the definition of accumulated cyclone energy [ACE], the influence of ENSO on TC intensity is examined. ACE leads ENSO indices: during the peak season (northern summer and fall), ACE is correlated approximately as strongly with ENSO indices up to six months later (northern winter), as well as simultaneously. Among lifetime, intensity, and number, the lifetime effect appears to be the most important to the ENSO signal.

26
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Western North Pacific Chen et al. (2004, Wea. Forecasting) Approximately 70% of WNP TC/TD genesis/development is linked to the monsoon gyre. The interannual variation of TC/TD genesis/development related to the monsoon gyre is highly correlated with that of the monsoon gyre activity (which is out of phase with that of the Nino-3 SSTs).

27
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Western North Pacific Ho et al. (2005, J. Geophysical Research) Cross-equatorial influence from the Southern Hemisphere (i.e., AAO) is comparable to that of ENSO. Main region of influence is different. Magnitude of composite difference of TC activity over the East China Sea toward west Japan with respect to the AAO phase is much larger than that related to ENSO phase. However, they didnt consider the coupled variability. El Niño minus La Niña TC passage numbers (#/year) Normal ENSO conditions only

28
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Western North Pacific Kim et al. (2005, J. Climate) Over the midlatitude East Asia, dominant interannual variability here is the dipole oscillation between south of Korea and southeast of Japan.

29
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Western North Pacific Xie et al. (2005, Geophysical Research Letters) The annual frequency of WNP typhoons and the number of landfall in China are negatively correlated with the Tibetan Plateau snow cover during the preceding winter and spring.

30
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Eastern and Central North Pacific ENP Elsner and Kara (1999) TC activity in the ENP tends to be opposite to that in the NA. Irwin and Davis (1999, Geophysical Research Letters), Kimberlain (1999, preprints) During El Niño years, changes in the warm SST regions lead to the westward shift in the genesis location of TCs in the ENP, resulting in the propagation of TCs father west into the central Pacific. Also, the lifetimes are longer during El Niño years relative to La Niña years. Collins and Mason (2000, Geophysical Research Letters) pointed out the need to study the ENP by subregions because environmental parameters affecting TC activity are different east and west of 116°W. CNP Chu and Wang (1997, J. Climate), Chu (2005) The vertical shear decreases over the tropical CNP during El Niño years, providing favorable conditions for TC development. In the non-El Niño years, most TCs follow a westward or northwestward track.

31
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – Australia and South Pacific TC activity in the Australian region is higher during La Niña years and below normal average during El Niño years. Nicholls (1979, Monthly Weather Review) The ENSO-TC relation is obtained from a strong correlation between the sea level pressure at Darwin, Australia, and TC days around the Australian region. Evans and Allan (1992, International J. Climatology) TC frequency near the date line increases during El Niño years. TC tracks in the tropical southwestern Pacific (west of the date line) became more zonal during El Niño years. In contrast, TCs tracked close to the coase of Queensland, Australia, and persisted southward with enhanced risk for coastal crossings during La Niña years. Basher and Zheng (1995, J. Climate) The incidence of TCs in the Coral Sea (west of 170°E) is influenced by local SST and east of 170°E the dominant control is not local SST but the eastward extent of ENSO-dependent atmospheric conditions (i.e., the monsoon trough).

32
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Interannual Variability – South Indian Ocean Jury (1993, Meteorol. Atmos. Phys.) The frequency of TC genesis in the Southwest IO increases during the east phase of QBO, but the impact of ENSO is not significant because of increased upper westerly shear, in spite of convection being enhanced during El Niño summers. Jury et al. (1999, J. Climate) The QBO is in phase with ENSO approximately every 4 years with the QBO leading every 4 months. The QBO periodically exerts a similar influence on the TC activity in the Southwest IO. Kuleshov and de Hoedt (2003, Bull.Aust. Meteorol. Ocean. Soc.) TC numbers are increased between 85 ° E and 105°E during La Niña years compared to El Niño years. Ho et al. (2006, J. Geophysical Research) During El Niño periods, TC genesis shifts westward, enhancing the TC formation west of 75 ° E and reducing east of 75 ° E. TC passages show a significant decrease in the southeast of Madagascar but a moderate increase in the central midlatitude South IO, indicating TCs move farther east during El Niño years.

33
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Recommendations We need more understandings about the coupled variability between the Northern (Southern) Hemisphere annular modes, ENSO and the MJO, and the variability related to the QBO. What is the coupled impact of the MJO and ENSO on TC activity? (Kim et al., in revision) Why does the QBO influence on NA hurricane activity weaken recent decades? Consideration of the annular modes and ENSO together may improve the skill of seasonal prediction of genesis, track, and landfall. Although ENSO is dominant factor on the interannual variability of basinwide-scale TC activity, its impact is variable by sub-basin regions. Need to verify the new hypothesis on the relationship, ENSO-TC, TPSC-TC. DEQ-PC hypothesis (Tang and Neelin 2004) Two-way interaction between TC and ENSO (Sobel and Camargo 2005) Role of Tibetan Plateau on TC activity (Xie et al. 2005)

34
Topic 4.1. Intraseasonal to Interannual Timescales6 th International Workshop on Tropical Cyclones Coupled impact of ENSO and the MJO

About project

Feedback

To ensure the functioning of the site, we use cookies. We share information about your activities on the site with our partners and Google partners: social networks and companies engaged in advertising and web analytics. For more information, see the Privacy Policy and Google Privacy &amp Terms.
Your consent to our cookies if you continue to use this website.